Even with journal arrangements for which thrust loading is not reasonably anticipated, and within which cylindrical bearings are appropriate to support radial loading, it is customary to utilize some structure by which to effect axial retention of the bearings that rotatably support a shaft, or the like. This is done so that should the shaft, even unexpectedly, apply a reasonable thrust load on the bearing, the bearing will remain seated within the housing. When the environment in which the journal arrangement is employed is such that both radial and thrust loading would be expected, one would generally consider the use of tapered bearing sets inasmuch as they effect excellent rotational support for a shaft subjected to such loading and without impairing rotation of the shaft. However, other alternatives are often employed because of the difficulties heretofore experienced in adjusting the axial end play of, or the preload on, the races which support the rollers in a tapered bearing assembly.
Thrust loading is transferred by the individual bearing assemblies in a tapered bearing set from the shaft to the journal box or housing, within which the bearings of the bearing set are supported. Generally, the inner race of each bearing assembly abuts a shoulder presented from the rotatable shaft. The outer race similarly abuts an opposed shoulder presented from the housing in which the bearing is supported. Obviously, the structure which presents the opposed shoulders between which the bearing set is captured, must be such as to permit assembly of the shaft and both bearing assemblies into the housing. Moreover, even if opposed, rigid shoulders could be provided, such an arrangement would not allow for any variation or adjustment in the end play of, or the preloading applied to, the bearing set.
To facilitate assembly, some arrangements (such as those wherein the hub of an axially elongated shaft is supported by inboard and outboard bearing assemblies) utilize the aforesaid configuration for the inboard bearing -- i.e., the inner race abuts a shoulder on the shaft and the outer race abuts a shoulder on the housing -- but reverses the arrangement for the outboard bearing. That is, the outer race of the outboard bearing would abut a shoulder on the housing and the inner race would abut a shoulder means presented from the shaft. In this latter arrangement, adjustment of the preload and the end play has been achieved by using a nut threaded onto the shaft to drive a washer which serves as the shoulder means. In this configuration, the washer abuts the inner race and the nut can be tightened or loosened to move the washer and thereby adjust the preload and end play.
It is, however, difficult to achieve and maintain incremental adjustments of the small magnitude desired by using a nut threaded onto the end of the shaft. Certainly, such nuts are often crenelated to permit a safety wire or clip to be inserted through a diametric bore in the shaft in order to secure the selected position of the nut. However, the magnitude of the adjustments permitted by the aforesaid arrangement is limited to a function of the thread pitch and the number of crenelations as well as their angular disposition.
To accomplish incremental adjustments of a small or fine magnitude, a variety of arrangements have been developed which utilize shims interposed between one race of the bearing set and a bearing retainer. The shims utilized by such prior art assemblies are available in a plurality of dimensions so that the selection of appropriately sized shims will generally achieve the desired end play or preloading. However, the installation of a typical shim assembly generally requires a rather complicated series of steps. For example, one must normally measure the gap between one race of the bearing assembly and the bearing retainer to determine the size of the shim or shims required, and the shim or a combination of shims must then be selected. The selected shim(s) must then be appropriately inserted between the selected race of the bearing assembly and the bearing retainer. The installation is not concluded until a final measurement has been made to verify that the proper end play and preloading has been achieved.
The installation of prior known shim assemblies is, therefore, a relatively complicated process for which considerable expertise is required, and for which shims must be available in a wide variety of sizes in order for the desired end play or preloading to be effected.
Another form of a prior art bearing adjusting assembly employs opposed cams or ramps. The use of cams or ramps allows for a wide range in the amount of end play or preloading adjustment available and reduces the number of components which must be stocked. However, the locking means heretofore employed in conjunction with cams or ramps to secure the selected adjustment, generally comprises a plurality of bolts that are receivable within threaded bores. The need to provide threaded bores, however, creates a problem in that while the aforementioned cams or ramps will allow for an infinite array of settings, discrete placement of threaded bores to receive the bolts severely restricts usage of the array to that permitted by the particular placement of the bores.